Adsorption Study of a Water Molecule on Vacancy-Defected Nonpolar CdS Surfaces

Abstract

A detailed understanding of the water–semiconductor interface is of major importance for elucidating the molecular interactions at the photocatalyst’s surface. Here, we studied the effect of vacancy defects on the adsorption of a water molecule on the (101̅0) and (112̅0) CdS surfaces, using spin-polarized density functional theory. We observed that the local spin polarization did not persist for most of the cationic vacancies on the surfaces, unlike in bulk, owing to surface reconstructions caused by displaced S atoms. This result suggests that cationic vacancies on these surfaces may not be the leading cause of the experimentally observed magnetism in CdS nanostructures. The surface vacancies are predominantly nonmagnetic except for one case, where a magnetic cationic vacancy is relatively stable due to constraints posed by the (101̅0) surface geometry. At this particular magnetic defect site, we found a very strong interaction with the H2O molecule leading to a case of chemisorption, where the local spin polarization vanishes concurrently. At the same defect site, adsorption of an O2 molecule was also simulated, and the results were found to be consistent with experimental electron paramagnetic resonance findings for powdered CdS. The anion vacancies on these surfaces were always found to be nonmagnetic and did not affect the water adsorption at these surfaces.

H2O molecule adsorption on s-triazine-based g-C3N4

“…As shown in Fig. 9(a)-(c), the cross-sectional profile of the optimized (6,6), (8,8) and (10,10) nanotubes is similar to regular hexagon, octagon and decagon, respectively. Outer diameters of these nanotubes are 8.49, 11.43 and 13.58 Å, respectively, in line with the values in other report [60].…”

“…Mulliken charge (e) Bond length (Å) H…N distance (Å) H1 O H2 O-H1 O-H2 (6,6) 0.49 -1.04 0.52 0.988 0.975 2.02 (8,8) 0.50 -1.04 0.52 0.988 0.975 2.09 (10,10) 0…”

“…Since experimental characterization fails in detecting individual molecules or groups on surface and observing the water-splitting process within extremely short time, this interaction is usually investigated by exploring the geometric and electronic property of H2O adsorption on material surface using density functional theory (DFT) calculation. To date, the H2O adsorption behavior on a series of photocatalysts has been reported, including TiO2 [5], CdS [6], ZnS [7], ZnO [8], WO3 [9], and vanadate [10,11].…”

Defect-Regulated Two-Dimensional Superlattice of Holey g-C3N4–TiO2 Nanohybrids: Contrasting Influence of Vacancy Content on Hybridization Impact and Photocatalyst Performance

“…Thus, the resulting roughening of the 2D g-C 3 N 4 nanosheet is responsible for the increase of layer thickness upon the increase of postcalcination temperature. Additionally, the presence of unpaired electron at these holes and vacancies allowed the formation of dangling bonds, leading to the enhanced adsorption of water molecules at the defect sites . The resulting enhancement of water adsorption on the surface of g-C 3 N 4 nanosheets was considered to make an additional contribution to the observed increase in the thickness of the nanosheet.…”

The valance state of vanadium-key factor in the flexibility of potassium vanadates structure as cathode materials in Li-ion batteries

“…Based on the area of the fitted curves, the relative atomic ratio of V 4+ /V 5+ present on the sample surface were estimated to be 0.10 for sample KVO-20 and 0.02 for sample KVO-40. The surface vacancies interact with the H 2 O molecules, which leads to water chemisorption 41 . Therefore, due to the 5-times smaller concertation of V-vacancy on the KVO-40 sample surface, the peak centered at 532.5 eV (chemisorbed OH − ions) is very likely to be overlapped with the peak located at 531.4 eV (OH–lattice).…”